Protein polymer having unfold activity on higher-order structure of protein

ABSTRACT

The invention of this application provides a protein polymer of 8 to 15 proteins in association, wherein each protein has the amino acid sequence of SEQ ID NO: 1, and where the protein polymer has an unfold activity on the higher-order structure of a protein and this protein polymer is useful for the development of therapeutic agents of various diseases due to the failure in the formation of the higher-order structure of a protein, and the like.

TECHNICAL FIELD

The present invention relates to a protein polymer having an unfold activity for the higher-order structure of a protein which has been intracellularly synthesized (unfold activity), which is useful for the development of therapeutic agents of various diseases due to the failure in the formation of the higher-order structure of a protein (protein aggregation and the like), and the like.

BACKGROUND ART

Amino acids synthesized in biological organisms can function as a protein, only when the polypeptide synthesized from amino acids can form the correct steric structure of the protein. Essentially, the correct formation of the steric structure is consistently, rapidly and efficiently done intracellularly. Cells have a factor promoting the formation of the higher-order structure, which is called the molecular chaperone. Some disadvantage for cells may sometimes occur, such as the insufficiency of molecular chaperone formation or protein denaturation due to the formation of an erroneous sequence. It has been elucidated recently that various diseases emerge because the control system for the higher-order structure of proteins does not work properly.

For example, Alzheimer's disease is a neuropathic disease occurring because the component called amyloid has aggregated together intracellularly. Amyloid generally forms a helix steric structure. In the case of the disease, however, the helix steric structure is transformed into a structure called, cross β structure. Thus, amyloid adheres to each other and accumulates intracellularly, triggering brain nerve damages. Furthermore, neuropathic Huntington's disease occurs, because elongated polyglutamic acid, which are attached to the tail part of the protein, huntintin, due to genetic mutation, is involved in the adhesion of the protein to each other, thereby leading to the failure of cellular functions. Furthermore, it is suggested that the functional impairment of HSP (HSC) as one of molecular chaperones is the pathogenesis of Parkinson's disease, cystic fibrosis, and in some cases of spinocerebellar degeneration.

It has been elucidated that a group of apparently different diseases such as these have the common molecular base, namely the failure in the formation of the higher-order structure of a protein as the underlining pathogenesis. No therapeutic method, which is extremely effective for these diseases, has existed yet. Because any component with an unfolding activity on the higher-order structure of a protein without substrate specificity has not yet been found, protein aggregates, which are the direct cause of such diseases, cannot be targeted and unfolded.

On the other hand, a cell should be so flexible that the structure of protein can be unfolded rapidly during dynamic movements, such as cell migration and cell division. Furthermore, once formed, protein aggregates with an erroneous higher-order structure are quickly unfolded, and transferred to a decomposition system. Although it has been recognized so far that such factor is essential, the factor has not yet been identified, because of the difficulty in the purification thereof.

So as to radically cure various diseases due to the failure in the formation of the higher-order structure of a protein, the aggregation of the diseased protein should essentially be untangled, as described above. It is indispensable therefore that “a factor for unfolding the higher-order structure of a protein” be identified, isolated and purified. Additionally, it is expected that such factor can be used as a very useful material for research in cell biology.

The invention of the application has been achieved in such circumstance. It is an object of the invention to provide a new protein polymer showing a great activity for unfolding the higher-order structure of a protein.

DISCLOSURE OF THE INVENTION

In a first aspect of the invention, the application provides a protein polymer of 8 to 15 proteins in association, each of the proteins having the amino acid sequence of SEQ ID NO: 1, wherein the protein polymer has an unfold activity for the higher-order structure of a protein.

In other words, the protein polymer in the first aspect of the invention (sometimes referred to as YDL178W protein polymer hereinafter) is a protein polymer of 8 to 15, preferably 10 to 12 proteins in association, wherein each protein of the protein polymer has the amino acid sequence of SEQ ID NO: 1 and is transcribed from the open reading frame (ORF) YDL178w (GenBank Accession No. Z74226) of Saccharomyces cervisiae.

In a second aspect of the invention, this application provides a protein polymer, wherein each of the proteins of the protein polymer has an amino acid sequence which has been modified from the amino acid sequence of SEQ ID NO: 1 by the deletion of one or more amino acid residues therein or the substitution of one or more amino acid residues therein with other amino acid residues or the addition of one or more amino acid residues thereto. The protein polymer in the second aspect of the invention is a protein polymer having variants of the protein transcribed from Saccharomyces cerevisiae ORF YDL178w or a protein transcribed from gene regions with homology to YDL178w in other yeast species or biological species, and has an unfold activity on the intracellular higher-order structure of a protein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron microscopic photopicture depicting the structure of the YDL178W polymer of the invention.

FIG. 2 shows the molecular weight of the YDL178W polymer of the invention as the results of the determination by size exclusion chromatography.

FIG. 3 is an electron microscopic photopicture depicting the structure of rabbit skeletal muscle myosin.

FIG. 4 is an electron microscopic photopicture depicting the structural change of myosin incubated with the YDL178W polymer of the invention.

FIG. 5 shows the molecular weight of the protein YDL178-del with deficiency in the coil-forming part as the results of the determination by size exclusion chromatography.

FIG. 6 shows the activity of the enzyme luciferase incubated with the YDL178W polymer of the invention or the protein monomer YDL178W-del.

BEST MODE FOR CARRYING OUT THE INVENTION

The protein polymer (YDL178W polymer) in the first aspect of the invention can be obtained by biochemical purification using unfolding activity as the marker of the unfold activity of the subject protein generated by Saccharomyces cerevisiae. However, its mass production by genetic engineering technology is preferable.

Specifically, recombination of a yeast expression vector using a DNA fragments encoding Saccharomyces cerevisiae ORF YDL178w (GenBank Accession No. Z74226) is done. Then, the recombinant vector is transferred into yeast. From the culture of the transformed yeast, the objective YDL178W polymer is isolated and purified, to thereby recover the objective YDL178W polymer at such an amount that the resulting YDL178W polymer can be used for example for the development of pharmaceutical products.

The recombinant vector can be introduced into yeast by well known methods such as lithium acetate method. So as to recover the objective protein polymer from the transformed yeast, further, a combination of well known processes can be done, including for example treatment with denaturing agents such as urea and surfactants, ultrasonic treatment, enzyme digestion, salting-out and solvent precipitation processes, dialysis, centrifugation, ultra-filtration, gel filtration, SDS-PAGE, isoelectric focusing, ion exchange chromatography, hydrophobic chromatography, affinity chromatography, and reverse phase chromatography. For purification in a simple manner and at high precision, the protein can be expressed while the protein is attached with an oligopeptide tag never influencing the unfold activity, as described below in the following examples.

The protein polymer in the second aspect of the invention can also be recovered by the genetic engineering approach as described above. Specifically, via screening of the genome libraries or cDNA libraries derived from other yeast species or biological species, using the polynucleotide encoding Saccharomyces cerevisiae ORF YDL178w or a partial sequence thereof as probe, a gene with homology to Saccharomyces cerevisiae ORF YDL178w is identified; then, transferring an expression vector recombined with the gene (polynucleotide) into a host cell, followed by isolation and purification from the culture of the resulting transformed host by know methods, the objective protein polymer can be obtained. Depending on the origin of the polynucleotide to be introduced and the like, a host cell can appropriately be used, including for example Escherichia coli, yeast, Bacillus subtilis, animal cells and plant cells.

EXAMPLES

The invention of this application is described in more detail and more specifically in the following examples. The following examples never limit the invention.

Example 1

A DNA sequence encoding a polypeptide of 6 histidine molecules was attached as a tag to the terminus of the DNA fragment encoding Saccharomyces cerevisiae ORF YDL178w. The resulting DNA fragment was inserted in a yeast expression vector pAUR123 (TaKaRa) to construct a recombinant vector, which was then introduced in yeast. Using the resistance against a drug (Aureobasidin; TaKaRa) as the marker, a transformed yeast strain was selected, which was then cultured in a yeast culture broth (YPD) supplemented with Aureobasidin at a concentration of 0.5 μg/ml. Subsequently, the cultured yeast was recovered, disrupted with glass beads and centrifuged to remove a fraction containing non-disrupted fragments, and was then ultra centrifuged at 100,000×g. The resulting precipitate was purified on a column packed with a resin specifically recognizing the histidine tag (Ni-NTA, Qiagen; or TALON, Clontech; or the like), to obtain the protein molecule generated from the yeast ORF YDL178w.

Example 2

The protein molecule derived from the yeast ORF YDL178w as recovered in Example 1 was treated by low angle rotation deposition method, which was then observed with electron microscope. As shown in FIG. 1, consequently, the protein molecule was of a doughnut shape or wrench shape with a hole at the center. It was confirmed that the protein molecule was a polymer of the protein monomers in assembly.

Further confirmation was carried out by size exclusion chromatography. As shown in FIG. 2, consequently, the molecular weight of the protein molecule was about 670 kDa. Because the molecular weight of the protein monomer transcribed from the yeast ORF YDL178w is about 60 kDa, it was confirmed that the protein molecule recovered in Example 1 was a polymer of 10 to 12 monomers in association, each of the monomers being the protein monomer YDL178W.

Example 3

The activity of the YDL178W polymer recovered in Example 1 for unfolding rabbit skeleton muscle-derived myosin was tested.

So as to observe one rabbit skeleton-derived myosin molecule with electron microscope, the sample was treated by the low angle rotary shadowing method. As shown in FIG. 3, myosin is of a characteristic higher-order structure with two heads and a tail.

The YDL178W polymer recovered in Example 1 was incubated with the myosin in the presence of ATP at 30° C. for 15 minutes, and was similarly treated by the low angle rotary shadowing method, for observation with electron microscope. As shown in FIG. 4, consequently, the structure of the myosin molecule was decomposed by the YDL178W polymer at such a state that the head almost completely lost the original shape and the helix structure of the tail was unfolded.

Example 4

It was confirmed via the analysis of the amino acid sequence of SEQ ID NO: 1 of the protein monomer encoded by the yeast ORF YDL178w that the protein contained a sequence for coil formation at the terminus (positions 1293 to 1593 in SEQ ID NO: 1). Because such coil structure is generally used as a tool for self-assembly of a protein, speculatively, the polymer structure of the YDL178W polymer would also be formed with the coil structure.

Therefore, the coil-forming sequence was deleted from the DNA sequence of the yeast ORF YDL178w. Then, the resulting deleted DNA fragment was expressed in yeast in a similar manner as in Example 1. The molecular weight of the resulting protein YDL189W-del was determined by size exclusion chromatography. Consequently, as shown in FIG. 5, the molecular weight of the resulting YDL189w-del was about 60 kDa, which is almost similar to the molecular weight of the monomer protein. Thus, it was confirmed that the protein with deficiency in the coil-forming part could not form any polymer.

Subsequently, the unfold activity on the higher-order structure of the protein YDL178w-del was studied. As the substrate, firefly luminescent enzyme luciferase was used, which was incubated in the presence of ATP with YDL178w-del or the YDL178W polymer. Luciferase allows the luminescence of luciferin via the enzyme activity, when the luciferase retains the higher-order structure. The luminescence can be detected with luminometer. As shown in FIG. 6, luciferase incubated with the YDL178W polymer never allowed the luminescence of luciferin. Hence, it was confirmed that the higher-order structure was unfolded with the YDL178W polymer. However, the luciferase incubated with the monomer protein YDL178W-del allowed the detection of the luminescence of luciferin at about the same level as that of control because the higher-order structure was not unfolded.

Based on the above results, it was verified that the formation of the polymer of the protein expressed from the yeast ORF YDL178w was indispensable, for exerting the unfold activity on the higher-order structure of a protein.

INDUSTRIAL APPLICABILITY

As described above in detail, the invention of this application can provide a protein polymer with an unfold activity on the higher-order structure of a protein. The protein polymer is useful for the development of therapeutic agents of various diseases due to the failure in the formation of the higher-order structure of a protein, and the like. 

1. A purified protein polymer comprising 8 to 15 proteins in coil formation, wherein each protein has the amino acid sequence of SEQ ID NO: 1, and the protein polymer has an unfold activity for a higher-order structure of a protein. 